In many areas of technology it is necessary to position objects relative to one another with high precision. This requirement also exists in the field of semiconductor technology, for example, during the testing of semiconductor components, which may be fabricated on semiconductor wafers. A plurality of semiconductor components of identical configuration are generally situated on a semiconductor wafer. In this case, so-called probers are used for testing the semiconductor components. For this purpose, contact pads are arranged at different locations in the semiconductor components (at the same location for each semiconductor component on the semiconductor wafer). During the testing with the probers, contact is made with the contact pads by the tips of contact-making needles in the probers.
By means of such contact-making, an electrical contact with the semiconductor component is produced, on the one hand to apply specific signals to the semiconductor component and on the other hand to measure the reaction to said signals.
According to setting methods in the prior art, the positioning of contact-making needle tips of a prober (referred to as a first object) relative to contact pads on the semiconductor component (referred to as the second object) is performed under optical or visual control. In such methods, the semiconductor component is observed visually from above by means of a microscope and the prober needle tips are then positioned onto corresponding contact pads under visual observation. If the contact needles happen to be set or positioned such that they lie on the contact pads of the semiconductor component, the setting operation is ended.
In some probers, it is also possible to mount the contact needles with a corresponding setting on a so-called needle card. A specific needle card is used for each type of a semiconductor component. In such cases it is then necessary to bring a further semiconductor component to be tested below the set contact-making needles so that the contact-making needles again make contact with the contact pads. If this has been done, the next test operation can be performed.
The positioning of each semiconductor component below a structure of contact needles may be done manually under visual observation using manual probers commonly known in the prior art. Automatic probers also are known. In the case of automatic probers, it may be possible for each semiconductor component to be brought automatically below the structure of contact-making needles if the distances or orientation of the needles and the semiconductor component is known (e.g., a rotation angle φ are known). In this case, the displacement of the semiconductor wafer required in order to perform an exact positioning may be calculated.
The visual or optical observation required for placing the needle tips on the contact pads may be performed by means of automatic image recognition systems. In this case, a pattern recognition is performed on or by an image of an observed region of the semiconductor component. The image may be recorded by a video camera, a CCD linear array or matrix or other image recording devices at a first instant. On account of the surface structure of the semiconductor component, the latter has a pattern. This pattern is significant for the component. If a further identical component is now to be tested, the latter then exhibits the same pattern. From the positional difference between the two patterns, the pattern recognition system can then determine geometrical correction values required to allow the semiconductor component that is currently to be tested to be positioned precisely below the needle structure by means of a positioning device.
In the context of the increasing miniaturization of the structures on the semiconductor components, considerable requirements or demands are made for the proper positioning of the semiconductor component with respect to the tips of the contact-making needles. The small widths of the miniaturized structures may be of the order of the wavelength of the light making it difficult or impossible to visually or optically resolve them to a sufficient extent. Thus, complex AFM probers, which operate according to the principle of atomic force microscopy (AFM), may be used for making contact with semiconductor component structures down in the range of 100 nm width. In this case, a contact-making needle is moved at a small distance above the surface of the semiconductor component, in particular in the region in which the contact pad is situated. As a result of the movement, the topography image of the region of the semiconductor surface is scanned on account of an interaction force occurring between the contact needle and the semiconductor surface. The exact position of the contact pad is may thus determined without the need for a visual observation.
The contact-making needle is referred to as a cantilever in the case of AFM probers. A piezo-drive is available for moving the cantilever, by means of which the cantilever executes a scan movement in order to obtain an image of the surface situated underneath, a scan. When the AFM prober is used, at a first instant, the region where contact is subsequently made is scanned by means of the cantilever. Once the scan is present, the tip of the cantilever is brought to the desired position determined and brought into contact at a second instant.
What is problematic in this case is that the semiconductor wafer and cantilever are exposed to thermal influences. This leads to a thermal drift in the time period between the first and second instants, i.e., expressed generally, a relative displacement arises between the first and second objects. In particular, this phenomenon occurs during the testing of semiconductor components under thermally controlled conditions. A so-called thermo-chuck is used in this case, which, on the one hand, fixedly clamps the semiconductor wafer during the test operation and, on the other hand, sets a desired temperature in a higher or lower temperature range in comparison with room temperature. The temperature alteration of the semiconductor wafer, for example on account of the thermal radiation, also influences the drive of the cantilever, as a result of which the drift occurs, which can no longer be disregarded in particular in the case of the small structure widths since, when making contact, the drift means that the cantilever no longer meets the position which was previously determined during the scan operation.
As is rapidly apparent, even thermostatic regulation of the surroundings cannot provide a remedy here since the drift is generated by the method itself. This problem area may also occur in other fields of application, in particular in the field of semiconductor technology, for example during bonding operations. Therefore, as a general proposition, a thermal drift or other drift between two objects can be problematic.
An object of the present invention is to prevent the disadvantageous influence of a thermal drift or other drift between a first and a second object during a positioning of a first object on a second object.